Abstract: Concrete is a typical quasi-brittle bonded granular material whose macroscopic mechanical response is jointly governed by cohesive and frictional properties. To quantitatively evaluate the evolution of these properties and the transition between the associated load-bearing mechanisms during loading, a mesoscopic simulation method for the cohesive-frictional behavior of concrete is developed using the discrete element method. According to bond integrity and interparticle contact states, particle contacts are classified into three categories: intact bonded contacts, post-failure closed frictional contacts and open contacts. This classification provides a basis for identifying the contact networks associated with cohesive and frictional load transfer. Using the average stress formulation based on contact forces and branch vectors, expressions are proposed for the total, cohesive, and frictional stresses averaged over a material volume element. These expressions allow the stress contributions of different contact categories to be evaluated separately and related to the overall mechanical response. A numerical model is subsequently established to characterize the cohesive and frictional mechanical properties of concrete in a decoupled manner. Model parameters are calibrated, and the numerical model is validated against experimental results obtained under uniaxial and conventional triaxial compression conditions. The results show that the pre-peak stress-strain behavior is primarily controlled by the network of intact bonded contacts, whereas the post-peak residual strength and deformation are predominantly governed by frictional load transfer through closed contacts after bond failure. Confining pressure suppresses crack opening and promotes the closure of contacts with failed bonds, thereby substantially increasing the contribution of frictional stress to the total stress and improving the stability of post-peak load-bearing behavior. During compression, concrete exhibits progressive degradation of cohesive resistance and gradual mobilization of frictional resistance, reflecting an evolving balance between the two mechanisms. The contribution of frictional resistance to the post-peak response becomes increasingly pronounced as confining pressure increases. The proposed mesoscopic simulation method provides a sound numerical basis for separating the cohesive and frictional mechanisms of concrete and analyzing damage evolution.